Use of phase change materials (PCMs) to mitigate early age thermal cracking in concrete: Theoretical considerations

- The article provides two numerical models dealing with the use of microencapsulated phase change materials to mitigate early age cracking in cement based materials.
- On the meso-scale, a discrete (lattice) model is developed and used to assess the thermal performance of a PCM-cement paste composite.
- On the structural-scale, a commercial FE package is used to calculate temperature and stress distributions in a wall-on-slab system.
- It is confirmed that the addition of microencapsulated phase change materials has great potential in reducing temperature and stresses in hardening massive concrete structures.

Phase change materials (PCMs) have found their use in concrete technology for increasing energy efficiency of building envelopes. In recent years, however, new potential applications for PCMs in concrete have been suggested, for example for reducing freeze-thaw damage and melting of ice forming on top of concrete pavements. A recent application of PCMs in concrete technology is their use for mitigating early-age cracking in hydrating concrete. The focus on this paper is therefore on theoretical considerations related to this particular application of phase change materials. In particular, the focus is on simulating microencapsulated PCMs, which show very promising experimental results. Numerical models are developed for 2 scales: the meso-scale, in which the PCM microcapsules are simulated as discrete inclusions in the cementitious matrix; and the macro-scale, where the effect of PCM microcapsule addition is considered in a smeared way. On the meso-scale, the effect of PCM volume percentage, their phase change temperature, and latent heat of fusion on simulated adiabatic heat evolution are assessed. On the macro-scale, influence of these parameters on the temperature evolution in semi-adiabatic (field) conditions and tensile stress development are simulated. The outcomes of this study provide valuable insights related to the influence of PCM microcapsule parameters on the behaviour of cementitious materials, enabling tailoring composites for different environmental conditions.